1. Field of the Invention
The present invention generally relates to a light-emitting device, and more particularly, to a backlight module and a light-emitting-diode (LED) package structure therefore.
2. Description of Related Art
A backlight module is usually classified into a side type and a direct type, wherein the side type requires a light-guiding plate to convert a linear light source into a planar light source required by a liquid crystal display (LCD) panel. In addition, because the LEDs have the advantages of higher color saturation, mercury-free material, higher lifespan, a lower operating temperature, and a variable color adjustment by a driven current, an LED array has gradually been implemented in the backlight module.
FIGS. 1A, 2A, and 3A respectively shows cross-sectional views of conventional Lambertian, Batwing, and side-type LED package structures. Moreover, FIGS. 1B, 2B and 3B respectively shows the relationship between the light intensity and scattering angles of the LED package structures shown in FIGS. 1A, 2A, and 3A.
Referring to FIG. 1A, the conventional Lambertian type LED package structure 100 comprises a substrate 110, an LED chip (not shown), a plastic package body 130, and two leading legs 140. In addition, the LED chip is disposed on the substrate 110 and covered by the plastic package body 130. Furthermore, the LED chip is electrically connected to one terminal of each of the leading legs 140 and accordingly electrically connected to other electronic components (not shown) through the terminal.
Referring to FIG. 2A, the conventional Batwing LED package structure 200 differs from the conventional Lambertian LED package structure 100 in that the plastic package body 130 of the Lambertian LED package structure 100 is of a hemispherical dome-shape (typically referred to as high dome), while the plastic package body 230 of the Batwing LED package structure 200 has a substantially hemispherical dome shape, but with a more planar top (typically referred to as low dome). Moreover, the plastic package body 330 of the side-type LED package structure 300, shown in FIG. 3A, usually has a funnel shape.
In comparison of these LED package structures as shown in FIGS. 1B, 2B, and 3B, light emitting from the Lambertian LED package structure 100 and the Batwing LED package structure 200 are more converged. Therefore, currently, most side-type backlight modules adopt Lambertian or Batwing LED package structure as a light source, which is briefly described in the following.
FIG. 4 shows a side cross-sectional view of a conventional side-type backlight module. Referring to FIG. 4, the conventional side-type backlight module 400 comprises a plurality of LED package structures 402 (FIG. 4 only shows one of these LED package structures 402) and a light-guiding plate 408. In addition, since light emitting from the LED package structures 402 is more converged, the backlight module 400 is usually added with a light-mixing element 404 so as to elongate a light-mixing distance of the LED package structures 402 and further to allow the backlight module 400 to provide uniformly mixed light.
Referring to FIG. 4, the LED package structure 402 is disposed close to a light incident cross section 410 of the light-mixing element 404. In addition, the light emitting from the LED package structures 402 is reflected into the light-mixing element 404 by using a light-emitting cross section of a emitting plate 420 attached to the LED package structures 402 and the light incident cross section 410 of the light-mixing element 404. Meanwhile, light emitting from the LED package structures 402 is then mixed in the light-mixing element 404 and emits through a light-emitting cross section 412 thereof, as well as into a light-converting element 406 connected between the light-mixing element 404 and the light-guiding plate 408. After that, light is reflected by the inner emitting surface 418 of the light-converting element 406 and passes through a light incident cross section 414 into the light-guiding plate 408. Eventually, the light emitting from a light-emitting cross section 416 of the light-guiding plate 408, provides the LCD panel with the light source.
From the preceding description, this type of backlight module requires a longer light-mixing distance for uniform mixing of the light emitting from the LED. Therefore, an integrated backlight module also requires a larger size. As a result, in today's trend of minimized display products, such a conventional backlight module is considerably limited in its applications.